Semiconductor device and method for manufacturing semiconductor device

Abstract

A semiconductor device includes a first electrode, a silicon carbide substrate having a first surface electrically connected with the first electrode and a second surface opposite to the first surface, an ohmic junction layer disposed on the second surface, and a second electrode disposed on the ohmic junction layer. The ohmic junction layer has a first layer that is directly disposed on the second surface and includes a first silicide of titanium and a first silicide of a metal element other than titanium, and a second layer that is directly disposed on the first layer, includes a second silicide of titanium and a second silicide of the metal element, and has a lower titanium concentration than the first layer.

What is claimed is: 
     
       1. A semiconductor device comprising:
 a first electrode; 
 a silicon carbide substrate having a first surface electrically connected with the first electrode, and a second surface opposite to the first surface; 
 an ohmic junction layer disposed on the second surface; and 
 a second electrode disposed on the ohmic junction layer, wherein the ohmic junction layer comprises 
 a first layer that is directly disposed on the second surface and includes a first silicide of titanium and a first silicide of a metal element other than titanium, and 
 a second layer that is directly disposed on the first layer, includes a second silicide of titanium and a second silicide of the metal element, and has a lower titanium concentration than the first layer. 
 
     
     
       2. The semiconductor device according to  claim 1 , wherein the metal element in the second layer has a concentration higher than that of the metal element in the first layer. 
     
     
       3. The semiconductor device according to  claim 1 , wherein each of the first layer and second layer includes carbon, and carbon in the first layer has a concentration higher than that of carbon in the second layer. 
     
     
       4. The semiconductor device according to  claim 1 , wherein silicon in the second layer has a concentration higher than that of silicon in the first layer. 
     
     
       5. The semiconductor device according to  claim 1 , wherein the metal element has a melting point lower than that of titanium. 
     
     
       6. The semiconductor device according to  claim 1 , wherein the metal element includes at least one from among nickel, molybdenum, tantalum, tungsten, palladium and cobalt. 
     
     
       7. A method for manufacturing a semiconductor device, comprising steps of:
 providing a substrate structure that includes a first electrode, and a silicon carbide substrate having a first surface electrically connected to the first electrode, and having a second surface opposite to the first surface; 
 forming a titanium layer on the second surface of the silicon carbide substrate; 
 forming a metal element layer including a metal element other than titanium that is bondable with silicon to form a silicide, on the titanium layer; 
 irradiating the metal element layer with laser light to form an ohmic junction layer having
 a first layer that includes a first silicide of titanium and a first silicide of the metal element other than titanium, directly disposed on the second surface of the silicon carbide substrate, and 
 a second layer that includes a second silicide of titanium and a second silicide of the metal element, directly disposed on the first layer, the second layer having a lower titanium concentration than the first layer; and 
 
 forming a second electrode on the ohmic junction layer. 
 
     
     
       8. The method according to  claim 7 , wherein the metal element in the second layer has a concentration higher than that of the metal element in the first layer. 
     
     
       9. The method according to  claim 7 , wherein each of the first layer and second layer includes carbon, and carbon in the first layer has a concentration higher than that of carbon in the second layer. 
     
     
       10. The method according to  claim 7 , wherein silicon in the second layer has a concentration higher than that of silicon in the first layer. 
     
     
       11. The method according to  claim 7 , wherein the metal element has a melting point lower than that of titanium. 
     
     
       12. The method according to  claim 7 , wherein the metal element includes at least one from among nickel, molybdenum, tantalum, tungsten, palladium and cobalt.